In Desktop, there may be a way, but I couldn't find it either.
As you may have already tried but found unhelpful,
at minimum all the sheets save the dashboard can be hidden
(by selecting hide on right-click of the sheet tab).
First of all, thanks for thinking along!
I was aware of the functionality to hide sheets from the ribbon. However, it seems that I can only hide those sheets which are presented on a dashboard (doesn't have to be the dashboard I selected, just any dashboard). I suppose you experience the same behavior?
To elaborate on my use case:
I have some sheets I'm still working on or just want to keep around for future reference. At the same time I want to demo in Presentation Mode with a clean view and show some of the 'finished' dashboards. I created a story with the relevant dashboards in there, yet I am still unable to hide the other sheets/dashboards. Especially when presenting a story the filmstrip/tabs bar isn't nice to have on screen as the navigation buttons for the story are near the top of the screen and as such you simply don't need to use the tabs at the bottom.
My apologies, I'd forgotten that un-dashboarded sheets can only be deleted.
I had hoped that the story would remove the bar, but we see it doesn't.
As you had, I checked as many settings as I could find, but was unable to turn
off that strip.
I suppose one suboptimal try would be to make a dummy dashboard, put
all the orphan sheets on it, then hide all the sheets (but the dummy dashboard
can't be hidden.)
We'll see what the community has to say.
You could submit an idea regarding this: